Q. Could you tell me what the Sig stands for in SigAlert? What constitutes a SigAlert as opposed to another tie-up?

– Karen McCaslin, Laguna Woods

A. Sig as in Loyd Sigmon, dig?

An executive at KMPC radio in L.A., he invented a device that allowed a police dispatcher to send out a message on an emergency that could affect traffic: A red light and buzzer let each station’s officials know a new message was in, and a button could be pressed to put the message on the air.

The first official SigAlert was on Sept. 5, 1955, when doctors and nurses were asked to help out with a train derailment in Los Angeles.

Nowadays, Caltrans and the California Highway Patrol use the term SigAlert to describe an unplanned occurrence that triggers the closing of at least one freeway lane for 30 minutes or more.

Q. I plan to camp again this summer at San Onofre State Beach park. I have a motorcycle with a 110cc engine that’s street legal on roads but not on freeways. I want to ride into San Clemente to pick up supplies on my motorcycle. But the park is isolated from the city except by the freeway. Would it be legal to enter the freeway and go one mile to an exit?

– Jack Hyatt, San Clemente

You need to scout out the on-ramps in the area for any signs prohibiting freeway travel with your “motor-driven cycle” (one with less than 150 cc).

Chris Johnson, a CHP officer and department spokesman, says state law allows bicycles on freeway shoulders and motor-driven cycles in freeway slow lanes – so long as there isn’t a black and white sign posted in the area prohibiting them.

Q. Caltrans recently began construction on the east- and westbound exits of the Riverside (91) Freeway at Weir Canyon Road. Three turn lanes on the ramps have been narrowed to one. This causes gridlock on the interchange, Santa Ana Canyon Road and the freeway. How long do we have to endure this?

– Jim Luft, Anaheim

By Wednesday, Caltrans hopes to hand all of the turn lanes over to the motoring public. Then Caltrans will mosey on down to the Gypsum Canyon Road exits for similar work, to take three weeks.

The ramps are part of a $14.2 million freeway project – cracked roadway will be replaced, for example – between Lakeview Avenue and the Riverside County line. The work began last month and is to be finished by year’s end.

Fact of the week: A Metrolink locomotive, with four coaches, gets one mile on 2-½ gallons of diesel. The engine holds 1,800 to 2,000 gallons.